The present invention relates to a melt-blowing head for supplying in a controlled manner either one or more polymeric materials to a melt-blowing die, either separately from one another or in a mixture thereof.
As known, the so-called melt-blown material, comprise a mass of polymeric material fibrils (for example polyolefine polymers, polyester polymers and copolymers thereof), extruded from a melt-blowing head having an extruding die and by using pressurized hot air jets.
Prior melt-blowing heads are conventionally provided with at least a suitably contoured inner chamber, receiving the mass of the polymeric material fed or supplied through an inlet channel, conveying the polymeric material inside the melt-blowing head.
However, the above mentioned method for supplying the polymeric material, i.e. from the mentioned inlet channel to the holes of the extruding die, does not allow to properly control the distribution of said polymeric material, thereby the polymeric material flow rate is affected by unevennesses, at the melt-blowing die level; moreover, also the holding time of the polymeric material in the melt-blowing head, and its temperature and pressure, and, in general, all the other operating parameters thereof are subjected to unevennesses.
Accordingly, at the outlet of the melt-blowing die, will be present a polymeric material which, for amount, temperature and melt index will be different from region to region, or through the melting die holes, thereby the fibrils generated by the air jet will have a length and a geometric shape which would be very different from region to region or from an assembly of holes to another assembly of holes of the die.
Accordingly, the end product (for example a non-woven fabric) formed by the mentioned fibrils would have a highly dishomogeneous construction, and, accordingly, uncontrollable chemical, physical characteristics.
This problem would be very serious for non woven fabric materials, of very broad diffusion, which have a lower specific gram weight.
Accordingly, the aim of the present invention is to provide a novel melt-blowing head specifically designed for providing a properly controlled supply of the polymeric material from the melt-blowing head inlet to the outlet of said polymeric material for the melt-blowing die.
Within the scope of the above mentioned aim, a main object of the present invention is to provide a melt-blowing head adapted to properly control the polymeric material flow-rate up to the melt-blowing die, to allow said polymeric material to be held inside the melt-blowing head for a holding time much less than that of prior melting heads, with a less risk of degrading said polymeric material.
The above-mentioned aim and object of the present invention, as well as yet other objects, which will become more apparent hereinafter, are achieved by the melt-blowing head as claimed in the accompanying claims.
Further features of the inventive melt-blowing head are defined in the dependent claims.
With respect to prior melt-blowing heads, the inventive melt-blowing head provide the advantage that it allows to properly control the polymeric material flow and distribution inside said melt-blowing head, thereby reducing to a minimum the holding time of said polymeric material in said melt-blowing head, and also reducing to a minimum possible degrading risks of said polymeric material.
Owing to the inventive melt-blowing head, in particular, the polymeric material will be supplied through a like distance from the inlet hole of the head up to any desired holes of the melt-blowing-die.
Thus, the polymeric material will be provided with the same heat amount and driving energy.